The present invention relates to surgical retractor support devices and, more particularly to a multi-position clamping mechanism for a surgical retractor.
In surgery that requires access to internal structures, retractors are often used to hold back tissue and expose the area in which the surgical operation is to be performed. A retractor typically includes a retractor blade and a retractor shaft upon which the retractor blade is mounted. The retractor is attached to a retractor support by a clamping device. The retractor support includes a rod which the retractor clamp can engage to connect the retractor to the retractor support.
An essential feature of any retractor clamp is that the clamp allow the retractors to be conveniently positioned on the retractor support and be adjustable as necessary to achieve appropriate positioning with respect to the area of surgical operation.
Various types of clamping devices have been proposed. Minnesota Scientific, Inc. is the assignee of U.S. Pat. Nos. 4,949,707, 5,020,195, 5,025,780, 5,242,240, 5,727,899, and 5,792,046, which are incorporated by reference. These patents relate to various improvements to the basic concept of holding two rod sections in an adjustable and fixable angular relationship relative to one another when locked in position. One of the rod sections is usually a retractor handle and the other is usually a rod section of a retractor support, which may be mounted to the operating table or other appropriate location.
Although, these clamping devices are believed to operate satisfactorily (i.e., to clamp two rod sections in a specific angular relationship), a need exists to provide the ability for at least one of the two rod sections to xe2x80x9csnapxe2x80x9d into a loosely gripped position to allow for precise positioning off the rod relative to the clamp before xe2x80x9cclampingxe2x80x9d the clamp into a securely locked position which prevents either of the two rod sections from moving relative to one another.
A need also exists to provide jaws for clamping members, which operate about pivot points to provide a scissors-like gripping action.
Furthermore, although the frustro-conical section provided in U.S. Pat. No. 4,949,707 provides one way to provide a large amount of surface area to resist twisting of the clamping members relative to one another when locked, an improvement is needed to securely position the two clamping members relative to one another in a locked position.
The retractor clamp preferably includes a drawbar extending at least partially through two clamping members which are rotatable relative to one another. The clamping members are comprised of a stationary jaw and a jaw movable about respective pivot points upon activation of a connected lever arm. The draw bar has an opening at its distal end for holding a dowel. The dowel fits within a cam nut such that when the draw bar is turned the cam activates the lever arms locking the clamps in a closed position.
A spring located in the lower clamping member biases the moveable arms such that the first and second jaws are biased to xe2x80x9csnapxe2x80x9d about an inserted rod section.
The two clamping members are separated by a lock bushing having a top disc and a bottom disc. The lock bushing has a preload spring between the top and lower disc. When the cam is not activated the preload spring prevents the top bushing and the lower bushing from engaging. This allows the two clamping members to rotate freely with respect to one another.
Additionally, the lock bushing top and bottom discs adjoin one another along cooperating serrations. The cooperating serrations engage one another when the drawbar is turned sufficiently to activate the cam, thereby locking the first and second clamping members in a fixed angular relationship relative to one another.